Why Acne Scars Occur

What is a scar exactly?

A scar is defined as the fibrous tissue that replaces normal tissue destroyed by injury or disease. In the normal healing process, cells undertake a repair process that includes breakdown of old tissue and production of new tissue. In most cases, this healing process results in a near perfect replication of the damaged tissue. Scars develop as a result of the body’s attempt to repair the surrounding tissue that has been wounded or injured where the healing process was unable to completely replace the lost or damaged tissue. Additionally, scar tissue — collagen — often forms a harder, more pronounced surface than regular healthy tissue. So basically, acne scarring is the result of damage in excess of what the body can normally heal, resulting in depressed or raised, hard, thickened areas of skin.

When a scar forms as a result of acne, it’s due to inflammation associated with the acne itself. As the inflammation extends deeper into the skin’s surface, more tissue damage occurs and the chance for scarring is greater.

The process of developing a scar can be broken down into 4 stages:

  1. Stage one

    Most people believe that acne is caused by several inciting events and it’s not always clear which event occurs first. However, it is well known that some combination of a) hyperkeratinization which is an overgrowth of epithelial cells that line the pores, b) increased production of sebum (sticky, oily substance made in the pores), c) growth of specific bacteria called P.acnes, and d) inflammation can start the acne cascade.1

  2. Stage two

    All of the factors contributing to the acne in Stage 1 trigger a release of proteins and enzymes that damage the local tissue.2

  3. Stage three

    The inflamed lesion opens and spills out into the surrounding tissue, releasing even more inflammatory chemicals.3

  4. Stage four

    The tissue starts to heal as new capillaries form, growth factors are released, new collagen is laid down, and some of it is “dissolved” by natural enzymes — so that eventually the skin appears normal. When this repair process cannot keep up with the degree of damage, it can develop into a scar.4


What type of
acne scars do I have?

Acne scars can come in a variety of shapes, sizes, and colors. While each case is different, there are 2 main types of acne scars to be aware of – atrophic scars and hypertrophic scars.5

Atrophic Scars occur when underlying collagen supporting the skin is lost. They usually take the form of a sunken hole in the skin, which has a pitted appearance.

There are 3 different categories of atrophic scars

  • Ice pick – Ice pick scars are typically deep and narrow, resembling little holes poked into your skin.
  • Boxcar – Boxcar scars are usually broader depressions with steep, defined edges.
  • Rolling – Rolling scars are broader depressions that have rounded sloping edges. They may or may not disappear when the skin is manually stretched.

Hypertrophic Scars are raised above the surrounding skin. Hypertrophic scars typically become raised lumps on the surface of the skin. There are actually 2 types of hypertrophic scars: keloid scars and regular hypertrophic scars.

For more detail on the difference between keloid scars and hypertrophic scars see Treatment Options.

Always consult with a medical professional to make sure you have the proper diagnosis and plan of action to safely achieve healthy skin.


2Goodman GJ, Baron JA. The management of postacne scarring. Dermatol Surg. 2007;33(10):1175–1188. [PubMed].

3Martin P, Leibovich SJ. Inflammatory cells during wound repair: the good, the bad and the ugly. Trends in Cell Biology. 2005;15(11):599–607.

4Stadelmann WK, Digenis AG, Tobin GR. Physiology and healing dynamics of chronic cutaneous wounds. American Journal of Surgery. 1998;176(2A):26S–38S. [PubMed].

5Chivot M, Pawin H, Beylot C, et al. Acne scars: epidemiology, physiopathology, clinical features and treatment. Annales de Dermatologie et de Vénéréologie. 2006;133(10):813–824. [PubMed].

SM 1976-9 Rev00

Footer Banner


Expert Q&A

Find acne scar insights, tips, and answers from our expert dermatologists.


Acne scar
treatment options

Learn about newer treatments for acne scars.


It all starts with love

I pledge to me to love myself — ALL of myself — from this day forward. And today I proclaim it.

Footer People Image